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Automation with PowerShell

Recurring tasks on the computer can be conveniently automated via shell script. You can choose from Bourne Shell (bsh), Bourne Again Shell (bash), C Shell (csh), Korn Shell (ksh), PowerShell and many more. But only PowerShell is available as an open source project cross-platform for Linux, macOS and Windows under the MIT license..

... By Markus Fleschutz 🕑 January 11, 2019

The command line

To try out PowerShell you need a text console. For this purpose, the convenient Windows Terminal (available for free in the Windows App Store) .

PowerShell offers the following commands, among others

cat filename - prints the contents of the specified file. cd folder- changes to the specified folder cd .. - changes one folder level higher clear - clears the display in console window cp source filename destination filename - copies the specified file date - displays the system time of the computer diff filename1 filename2 - shows the difference of both files echo text - prints the specified text echo $Variable - outputs the content of the given variable exit - exits the PowerShell console or the PowerShell script help - displays help for PowerShell cmdlets and concepts (very helpful !!!) history - shows the commands entered so far hostname - prints the name of the computer kill process ID - kills the specified process ls - lists the contents of a file folder mkdir folder name - creates a folder with the specified name mv source filename destination filename - moves the specified file ping hostnameIP address - checks if the specified computer is reachable on the network ps - lists all currently running processes pwd - prints the current file path rm filename - deletes the specified file or folder (!) set variable name value - sets the given variable to the given value sleep seconds - waits the specified number of seconds wget URL - downloads the specified file from the Internet

cmdlets

The above commands are actually aliases to so-called cmdlets. Cmdlets always consist of a verb, a hyphen and a noun, for example Get-ChildItem (show file folder). You can use Get-Command and Show-Command to search for and find cmdlets. Which cmdlets are available depends not only on the PowerShell version used, but also on the operating system and the additional software equipment installed. Cmdlets are basically located in modules.

Writing PowerShell scripts

Using any text editor, create a new file named HelloWorld.ps1 with the following content

echo Hello World!
sleep 10

Then save the file and select Run with PowerShell with a right click. The script will be executed.

PowerShell features

PowerShell is powerful! PowerShell's capabilities almost approach a programming language. And the examples below work both in a PowerShell script and in the PowerShell console. So just try them out!

Example 1 Variables & Numbers

$PI = 3.1415927
echo $PI

Example 2 Variables & text

$var = Hello 
$var += John
echo $var

Example 3 Variables & Text Arrays

$days = Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday
foreach($day in $days) {
	echo $day
}

Example 4 Initialize multiple variables

$a = $b = $c = 1
echo $a, $b, $c

$a, $b, $c = 1, 2, 3
echo $a, $b, $c

Example 5 Variables & program output

$output = ls
echo $output

Example 6 for loops

for($i = 0; $i -le 100; $i++) {
	echo Hello
}

Example 7 foreach loops

$colors = red, green, blue
foreach($color in $colors) {
	echo $color
}

Example 8 do-while loops

do {
	echo Hello
} while ($false)

Example 9 while loops

while ($true) {
    echo Hello
    break
}

Example 10 Infinite loops

while ($true) {
	echo ENDLESS
}

Example 11 Comments

# comment
1 + 1 # should make 2

Example 12 Comparison operators

1 -eq 1 # is equal
0 -ne 1 # is not equal
0 -lt 1 # is less than
0 -le 1 # is less than or equal to
1 -gt 0 # is greater than
1 -ge 0 # is greater than or equal to
PowerShell -like Pow # comparison with wildcards (opposite -notlike)
Jan, Feb, March -contains Feb # comparison with arrays (opposite -notcontains)